Topic

#Dating and isotopes

How scientists measure the age and origin of meteorites using isotopes.

Lessons (8)

Classifying a new meteoriteThis final lesson brings the course together, following a new meteorite from arrival at the laboratory to an approved name in the Meteoritic
How meteorites are datedMeteorites carry several clocks at once. Read correctly, they tell us when a rock formed, when it was knocked off its parent body and when i
Early Solar System chronologyMeteorites let us build a timeline of the first few million years of the Solar System with a precision that seems almost impossible. Here is
Enstatite chondrites and other rare classesBeyond ordinary and carbonaceous chondrites lie smaller classes formed in very different chemical conditions. They show how varied the early
Martian meteorites in depthMartian meteorites are our only samples of Mars. Their petrology, ages and isotopes reveal the planet's volcanic history, water and atmo
Oxygen isotopes: the fingerprint of originOxygen makes up nearly half of most rocks by mass, and its three stable isotopes carry a signature that distinguishes parent bodies.
Primitive achondrites and ureilitesBetween chondrites and fully melted achondrites lie rocks caught in the act of melting. They reveal how differentiation begins.
The NC–CC isotopic dichotomyNucleosynthetic isotope anomalies split meteorites into two great families that formed in separate regions of the disc.

Courses (12)

Exponential decay and radiometric agesRadioactive decay is exponential, and the decay equation can be turned into an age equation. This lesson derives it and uses uranium–lead to
Extinct radionuclides and the first few million yearsSome radioactive isotopes present when the Solar System formed have long since decayed away.
Mass spectrometry and oxygen isotopesMass spectrometers measure isotope ratios to within about ten parts per million. Oxygen's three isotopes then sort meteorites into famil
Orbits, Kepler's laws and resonancesKepler's third law connects an asteroid's distance from the Sun to its orbital period.
A-level: The physics and chemistry of meteoritesTwelve lessons that apply A-level physics, chemistry and geology to meteorites: gravitational fields and Kepler's laws, impact and entry
Chondrites and the birth of the Solar SystemChondrites are the least changed rocks we have. Their components formed in the disc around the young Sun and date the start of the Solar Sys
Dating meteoritesA meteorite has several ages: when it formed, when it was broken off its parent body, and how long it has been on Earth.
Rocks from the Moon and MarsSeveral hundred meteorites are pieces of the Moon or Mars, thrown off by impacts. This lesson explains how they were identified and what the
The journey from the asteroid beltMost meteorites begin as fragments of asteroids between Mars and Jupiter. This lesson follows the long, slow route that brings a few of them
Half-life and dating meteoritesRadioactive isotopes decay at a steady, predictable rate. Measuring how much has decayed in a meteorite tells us how long ago it formed.
Isotopes as fingerprintsAtoms of the same element can have different numbers of neutrons. The ratios of these isotopes in a meteorite act like a fingerprint for the
GCSE: Meteorites across the sciencesTwelve lessons that use meteorites to practise GCSE physics, chemistry and biology: the formation of the Solar System, isotopes and half-lif

Teachers (2)

Modelling half-life with diceDoes a random process produce a predictable half-life, and how does sample size affect how well the model fits? The age of the Solar System,
Scheme of work: meteorites from Key Stage 1 to A-levelHow free meteorite lesson plans, courses, interactive tools, projects and reference sections map to each key stage of the National Curriculu

Explainers (4)

How a rock leaves Mars and reaches EarthFrom an asteroid impact on Mars to a stone in the desert: how Martian meteorites make the journey, and how we know where they came from.
How chondrules formedTiny frozen droplets fill most stony meteorites. What melted them is one of the oldest puzzles in meteoritics; here are the clues and the le
How meteorites are classifiedFrom stone, iron or stony-iron down to a code like L6 S4 W2: the questions scientists ask, in order, to place a new meteorite in its group.
Radiometric dating and isochronsHow radioactive atoms act as clocks, why an isochron gets round the problem of the starting amount, and how meteorites gave the age of the S

Books (2)

Meteorite Classification: The Professional's GuideA working reference for classifiers, curators and postgraduate researchers. It sets out current practice for every meteorite type: the fifte
Meteoritics for StudentsMeteorites are the oldest rocks we can hold, and reading them uses nuclear physics, chemistry, geology and orbital mechanics. This guide run

Meteorite types (19)

AcapulcoitesFine-grained rocks that only just began to melt. Named after Acapulco in Mexico, which fell in 1976, acapulcoites are fine-grained rocks of
BrachinitesOlivine-rich rocks from an asteroid whose melt drained away. Named after Brachina in South Australia, brachinites are made mostly of iron-ri
Carbonaceous chondritesRare, often dark chondrites rich in carbon, water-bearing minerals and organic compounds, including the building blocks of life.
ChondritesPrimitive stones that never melted, made of the first solids of the Solar System. The most common meteorites of all.
CK chondritesHeated, highly oxidised carbonaceous chondrites, cousins of the CVs. CK chondrites, named after Karoonda in Australia, are unusual among car
CO chondritesSmall-chondrule carbonaceous chondrites, close relatives of the CMs. CO chondrites, named after Ornans in France, have very small chondrules
CV chondritesLarge chondrules and big white inclusions, the oldest solids in the Solar System. Allende is the classic.
EH chondritesHigh-iron enstatite chondrites. EH chondrites have more metal and smaller chondrules than EL chondrites, and contain niningerite, a magnesiu
Enstatite chondritesChondrites formed with almost no oxygen to spare, full of rare minerals unknown on Earth's surface.
H chondritesHigh-iron ordinary chondrites: about a third of all meteorites seen to fall. H chondrites have the highest total iron of the ordinary chondr
IAB ironsIrons with stony inclusions, from a partly melted asteroid. Canyon Diablo and Campo del Cielo.
IIE ironsIrons full of silicate fragments, possibly from asteroid Hebe. IIE irons are octahedrites of varying coarseness that often contain silicate
K chondrites (Kakangari grouplet)A tiny grouplet with a mix of features found in no other chondrite group. K chondrites are named after Kakangari in India, which fell in 189
Martian meteoritesRocks from Mars, recognised by gas from the Martian atmosphere trapped inside them.
Primitive achondritesRocks that began to melt but were never fully processed: halfway between chondrites and igneous rocks.
Pyroxene and ungrouped pallasitesPallasites that fit neither main group nor Eagle Station, among them the pyroxene-bearing pair Vermillion and Yamato 8451.
R chondrites (rumurutiites)Highly oxidised chondrites with almost no metal. R chondrites are named after Rumuruti in Kenya, the only one seen to fall (1934).
Ungrouped achondritesMelted rocks that match no known group: each may be the only sample of its own world. Some achondrites fit none of the named groups.
WinonaitesPrimitive achondrites related to the silicate inclusions in IAB irons. Named after the Winona meteorite, found buried in a Sinagua ruin in A

Space missions (1)

GenesisA sample of the Sun itself, which survived a crash landing and rewrote the Solar System's oxygen story.

Meteorite minerals (2)

MoissaniteSilicon carbide; its microscopic grains in chondrites are stardust older than the Sun. Moissanite is silicon carbide, almost as hard as diam
TroiliteIron sulphide, the bronze mineral found in almost every meteorite. Troilite is iron sulphide with exactly one iron atom for every sulphur at

Glossary (55)

Questions and answers (22)

Can meteorites tell us how the Sun was born?Yes. Isotopes in meteorites suggest the Sun formed in a cluster of stars, possibly near massive stars that added short-lived radioactive ele
Do meteorites contain stardust older than the Sun?Yes. Primitive meteorites contain tiny presolar grains that formed around other stars before the Sun existed.
How can I explain the age of the Earth using meteorites?In 1956 the American scientist Clair Patterson used lead in meteorites to calculate an age of about 4.55 billion years for Earth and the Sol
How can I teach half-life using a classroom model?Use dice, coins or sweets: each round, remove the ones that 'decay' and plot how many remain. Pupils see the halving pattern and the
How can I use meteorites in chemistry lessons?Meteorites show elements and compounds in nature: iron-nickel alloys, silicates, sulfides and even organic molecules, and they link to the o
How do meteorites reveal the early Sun's activity?Solar wind gases, solar flare tracks and isotopes made by solar radiation in meteorites record that the young Sun was far more active than t
How do scientists cut and study a meteorite?They cut meteorites with diamond saws, prepare polished slices and thin sections, and analyse them with microscopes, electron beams and mass
How do scientists date a meteorite?Scientists measure the products of natural radioactive decay in a meteorite's minerals, using several 'clocks' such as uranium-l
How do scientists stop meteorites being contaminated?By collecting fresh falls quickly with clean tools, storing samples in dry nitrogen or vacuum, using clean rooms, and checking isotopes to t
How do scientists tell which parent body a meteorite came from?Mainly by oxygen isotopes, which act like a fingerprint, together with chemistry, mineralogy and other isotope systems that group meteorites
How do we know a meteorite came from Mars?Gas trapped in glass inside some Martian meteorites matches the unusual atmosphere measured on Mars by the Viking landers in 1976.
What age is right to start teaching about meteorites?Any age. Children as young as four or five enjoy shooting stars and space rocks, and the topic can deepen all the way to university level.
What are short-lived radioactive isotopes and why do they matter?They are radioactive isotopes with half-lives of millions of years or less that existed in the early Solar System.
What can meteorites tell us about the Moon's origin?Lunar meteorites and comparisons with other meteorites show the Moon is chemically very similar to Earth, supporting a giant impact origin,
What is a brachinite?A brachinite is a rare olivine-rich achondrite, thought to be the residue left after an early asteroid partly melted and lost its basaltic m
What is a calcium-aluminium-rich inclusion (CAI)?A CAI is a pale inclusion in some chondrites made of high-temperature minerals. CAIs are the oldest solids formed in the Solar System, about
What is a cosmic-ray exposure age?A cosmic-ray exposure age is the length of time a meteorite spent as a small body in space, exposed to cosmic rays, between breaking off its
What is an angrite and why is it important?Angrites are rare volcanic meteorites, among the oldest igneous rocks known, crystallising within a few million years of the Solar System&#3
What is an enstatite chondrite?An enstatite chondrite is a chondrite made mostly of iron-free enstatite pyroxene, formed in very oxygen-poor conditions, with isotopes simi
What is the cosmic-ray exposure age of most meteorites?Most stony meteorites travelled as small bodies for about 1 to 100 million years; iron meteorites typically for hundreds of millions of year
What is the isotopic dichotomy in meteorites?It is the division of meteorites into two isotopic families, from the inner and outer Solar System, which stayed separate for millions of ye
Why do iron meteorites come from so many parent bodies?Iron meteorites come from the cores of many small planetesimals that melted early; their strength lets them survive while the rocky outer la

Micrometeorites (2)

What micrometeorites reveal about the early Solar SystemMicrometeorites carry material from many more comets and asteroids than the meteorites in our museums, including fragile, carbon-rich bodies
Catching space dust in the stratosphereThe smallest space dust can be caught before it ever touches the ground. Since the 1970s, high-flying aircraft have collected interplanetary

People (4)

Gerald WasserburgThe Caltech geochemist whose super-clean laboratory dated Moon rocks and found the traces of aluminium-26 in the Allende meteorite.
Harold UreyThe Nobel prize-winning chemist who helped found cosmochemistry, the study of the chemistry of the Solar System.
Robert ClaytonThe chemist who discovered that oxygen isotopes give every meteorite group its own fingerprint, the key to telling where meteorites come fro
Toshiko MayedaThe chemist who, with Robert Clayton, measured the oxygen isotopes of meteorites from every part of the Solar System.